1. Field of the Invention
The invention, in general, relates to an automotive vehicle provided with a plurality of wheels suspended by torsion bars and, more particularly, to vehicles of the kind equipped with wheels resiliently suspended by torsion bars extending substantially transversely of the vehicle and consisting of a pair of concentrically arranged internal and external torsion springs with a wheel-supporting road arm cooperating with one end of the internal and external torsion springs. The invention is of particular advantage for use in track-laying vehicles.
2. The Prior Art
U.S. Pat. No. 3,913,939 issued Oct. 21, 1975 to Sinclair et al. discloses a wheel suspension for track-laying vehicles, such as combat tanks, having wheels mounted on road arms and supported by pairs of coaxial torsion springs. As disclosed, each road arm is connected to an end of only the internal torsion bar the other end of which is journalled for rotation in an anchor element affixed to the hull of the vehicle. The anchor element is provided with a lever or height control arm connected to a rod which in turn is connected to an hydraulic cylinder or ram. Furthermore, an end of an external torque tube is rigidly mounted to the anchoring element for rotation therewith, its other end being connectable with the road arm by way of a lost motion device.
If the hydraulic system disclosed for use with that suspension fails, or if the rod breaks, the internal torsion bar will rotate freely because the external torque tube is also connected to the road arm. Thus, in case of a systems failure, the vehicle is rendered defunct. The only function of the lost motion device is that when the system is operative, the external torque tube will lend added support to the internal torsion bar, but only after it has rotated by an amount predetermined by the angular disposition of the height control arm. This is demonstrated by an abrupt change in its characteristic curve. Hence, the hardness of the spring suspension cannot be set independently of the angular disposition of the road arm, as a function of the deflection of the spring. Moreover, certain driving conditions mandate selectively variable wheel loads. These cannot be attained by means of the disclosed rod connection.